Process for producing high-grade half stuff



Patented Dec. 28, 1926.

UNITED STATES PATENT OFFICE.

HERMANN WENZL, or FRANKFORT-O1\T-THE-MAINSUD, GERMANY, ASSIGNOR TO THE FIRM I. e. FARBEIENDUSTRIE-AKTIENGESELLSCI-IAFT, or FRANKFORT-ON-THE- MAIN, GERMANY.

PROCESS FOR PRODUCING HIGH-GRADE HALF STUFF.

No Drawing. Application filed July 8, 1926, Serial No. 121,271, and in Germany January 25, 1926.

the flax-harvest, to paper raw-stuff, al-

though their high contents of valuable cellulose and the intact-mess and long-fibrousness of the flax fiber afford the best prospects for utilizing the said wastes. For instance, Sidney D. Wells and Earl R. Schafer in the preface to their paper on Chemical Constituents of Flax Straw in the Paper Trade Journal, Vol. LXXX, No 17 of April 23, 1925, page -47 say what follows These studies indicate that the com-' pounds of the stem of the flax plant known to the textile and allied trades as bast and shive are widely difierent-in their chemical characteristics. The bast seems to consist of relatively pure cellulose adsorbed to which are carbohydrates soluble in hot water or mild alkaline treatment while the shive is composed of cellulose in close combination with pentosans and lignin. A large number of various treatments failed to indicate any that were capable of softening or disintegrating the shive without marked reduction in the tensile strength of the bast, and on page 50 of the conclusions they say: That chemical methods exist which are capable of pulping the shive without weakening the bast has not yet come to the attention of the writers.

From this up-to-date quotation it appears with absolute certainty that the .dishomogeneous composition of many raw fibrous substances, especially of spinning-mill wastes or other similar cellulosic wastes prohibits a chemical resolution by means of the methods hitherto known.

The object of my present invention is to resolve the raw materials referred to without injuring the strength of the fiber or reducing the output to an undesired degree. This object is attained by a novel composition of the resolving liquor, as more ully explained in the following description.

Substituting magnesium. or sodium for calcium in the usual digesting liquors of the cellulose manufacture is well known. Kelnesium chloride.

ler has already in the beginning of the seventies of the past century proposed to employ sodiumbisulphite, and Graham,

British Patent No. 5365/1882, uses neutral sodium sulphite to which subsequently sulphurous acid is added, so that sodium bisulphite is formed in the course of the process which then acts together with sulphlte.

In contradistinction to this the resent invention is based on the discovery t at the composition of the digesting liquor in View of its two components: bisulphite and sulphite, must from the first correspond to a certain relation, and that excellent results I are obtained by following the relation XI-ISQ :X SO =3.0 to 3.5 parts :1 part.

' tered.

Furthermore certain neutral salts are to be added to the digesting liquor above described, the said neutral salts, facilitating the extraction of the incrustations without themselves participating in as it seems,

the chemical reaction. Preferably neutral salts may be used which in aqueous solution at elevated temperature are subject to hydrolytic dissociation.

My process is, by way of example, carried out in the following manner 10000 kgs. of spinning-mill wastes (flax straw) are mixed in an acid-proof rotary ,digester with 35000 liters of a solution con taining 1800 kgs. of sodium-bisulphite, 540

kgs. of sodium 'sulphite, and kgs. of magnesium chloride. The digester is closed and, under continuous revolution, left for half an hour without heating. I A neutral,

alkali metal salt as alkali sulnhate'may be added instead of or in addition to mag- ;Hereupon it is slowly heated steam. up to C. and leftat this perature for about 1 hour. After this time the temperature is gradually raised to by live I ceeding 100 expelled under pressure; the dige 150 0., and after 10 hours the liquid is (1 ma terial is several times washed with water and hereafter further treated in the usual way. In this manner a pure half stulf is obtained which is easily bleachable to a pure white and possesses a most satisfactory strength.

treatment of manila, hemp, jute waste and the like, provided that the added neutral salts and the concentration of the digesting liquid are adapted to the material just treated; straw of grain may also be subjected to pulping according to my invention.

Instead of immediately treating the fiber with the digesting liquid, as described in the above example, I may also proceed in the following manner :--The fibrous material is first impregnated with a substantially stronger solution of the same composition as indicated, then the excess of liquid is mechanically separated, and now the material is treated with steam under pressure 'at elevated temperature, so that the concen tration of the impregnating liquid gradually passes over to that of the digesting liquid.

I claim Y 1. The process of producing high-grade half stuff, especially from spinning-mill waste, flax, hemp straw, jute and the like, comprising the digesting of the raw materials at an elevated temperature with an aqueous solution containing one part of a monosulphite to between 3 and 3.5 arts of a bisulphite withthe addition of a so uble neutral salt.

2. 'The process of producing high-grade half stufi, especially from spinning-mill waste, flax, hemp straw, jute and the like, comprising the digesting of the raw materials with a concentrated aqueous solution containing one part of a monosul hite to between 3 and 3.5 parts of a bisulphlte with the'addition of a soluble neutral salt mechanically separating the excess of the solution, and treating the material with steam under Cpressure at temperatures ex- 3. The i{process of producing high-grade half stu especially from spinning-mill waste, flax, hemp straw, jute and the like, comprising the digesting of the raw materials at an elevated'temperature with .an

aqueous solution containing one. part of a monosul bite to between 3 and 3.5 parts of a his phite with the addition of a soluble neutral salt subject to hydrolytic dissociation in aqueous solution at elevated temperature.

4:. The process of producing high grade.

half stufl, especially from spinning-mill waste, flax, hemp straw, jute and the like, comprising the digesting of the raw materials with a concentrated aqueous solution containing one part of a monosulphite to between 3 and 3.5 parts of a bisulphite with the addition of a soluble neutral salt subject to hydrolytic dissociation in aqueous I solution at elevated temperature, mechanic- Thelnvention is also applicable to the ally separating the excess of the solution, and treating the material with steam under pressure at temperatures exceeding 100 C.

5. The process of producing high-grade half stufl', especially from spinning-mill waste, flax, hemp straw, jute and the like, comprising the digesting of the raw materials at an elevated temperature with an aqueous solution containing one part of sodium sulphite to between 3 and 3.5 parts of sodium bisulphite, with the addition of a further neutral soluble alkali salt and magnesium chloride.

6. The process of producing high-grade half stuff, especially from spinning-mill waste, flax, hemp straw, jute and the like, comprising the digesting of the raw materials at an elevated temperaturewith an aqueous solution containing one part of a monosulphite to between 3 and 3.5 parts of a bisulphite with the addition ofl an alkali sulphate and magnesium chloride.

7. The process of producing high-grade x half stuff, especially from spinning-mill Waste, flax, hemp straw, jute and the like, comprising the digesting of the raw materials at an elevated temperature with an aqueous solution containing one part of sodium sulphite to between 3 and 3.5 parts of sodium bisulphite, with the addition of an alkali sulphate and magnesium chloride.

8. The process of producing high-grade half stufi', especially from. spinning-mill waste, flax, hemp straw, jute and the like, comprising the digesting of the raw materials at an elevated temperature with an aqueous solution containing one part of a monosulphite to between 3 and 3.5 parts of a bisulphite with the addition of-magnesium chloride.

9.'The process of producing high-grade .half stufi, especially from spinning-mill waste, flax, hemp straw, jute and the like, comprising'the digesting of the raw materials with a concentrated aqueous solution containing one part of a monosulphite to between 3 and 3.5 parts of a bisulphite with the addition of magnesium chloride, mechanically separating the excess of the solution, and treating the material with steam underopres sure at temperatures exceeding 100 4 In testimony whereof I alfix my signature.

' HEBMANN' WENZL. 

